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<title>GrADS Command: open</title>
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<h2><b>open</b></h2>
<p>
<code>open <i>filename</i></code>
<p>
Opens <code><i>filename</i></code>, which should be the name of a
GrADS data descriptor file, also called a control file.
<p>
<h3>Usage Notes</h3>
<p>
<ol>
<li>The standard file extension for Grads data descriptor files is
<code>.ctl</code>. Provided you adhere to this standard, there is no
need to type the extension <code>.ctl</code> when issuing the
<code>open</code> command.
<p>
<li>You will need to open at least one data-descriptor file before
you can enter other GrADS commands.
<p>
<li>You can open more than one data-descriptor file.   Each file is
numbered according to the order in which it was opened.
</ol>

<p>
<h3>Examples </h3>

<p>
<code>
open jandata.1966<br>
open jandata.1966.ctl
</code>
</ul><p>

<p>
Both of these commands will have the same effect -- opening the GrADS
data descriptor file <code>"jandata.1966.ctl"</code>.


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